This study is being undertaken to better explain the decreases in dental caries prevalence in non-fluoridated areas and to determine reasons for any increases in dental fluorosis. The study will include the collection of comprehensive data on exposure to fluoride from all sources by children and adolescents. Two communities located in a geographic region classified as a "high fluoridation" area -- one with a central water supply which is "fluoride deficient" (<0.3 ppm fluoride) and one which has been optimally fluoridated continuously since 1980 or earlier--will be selected for study. Within each community approximately 400 (ages 12 and 13 years) life-long residents will be asked to participate in the study. These subjects will receive a clinical oral examination for dental caries and enamel fluorosis. Samples of plaque, saliva, blood and urine will be collected from the subjects and evaluated for their fluoride concentrations in the laboratory. All subjects will receive a dietary collection instrument and a detailed questionnaire on residence and fluoride-use history, as well as sociodemographic, and behavioral information. In addition, water samples will be collected from community sites and school buildings for analysis; and frequently consumed foods, as listed in the dietary histories, will be purchased locally and analyzed for fluoride content. Fluoride distribution in body fluids and tissues will be correlated with each other and with reported intake, clinical findings of dental enamel fluorosis, and dental caries experience. These relationships will be evaluated between the communities and between groups of individuals with different fluorosis manifestations.